Determination of Penetration Depth of Transverse Spin Current in Ferromagnetic Metals by Spin Pumping

TL;DR

This paper investigates how the transverse spin current penetrates ferromagnetic metals by analyzing ferromagnetic resonance line widths, providing experimental measurements of penetration depths in various ferromagnetic materials.

Contribution

It introduces a method to determine the transverse spin current penetration depth using FMR spectra analysis, combining theoretical and experimental approaches.

Findings

Penetration depths in NiFe, CoFe, and CoFeB were 3.7 nm, 2.5 nm, and 12.0 nm respectively.

FMR line widths depend on ferromagnetic layer thickness, not in resonance with the magnetic field.

The method allows for quantitative assessment of spin current behavior in ferromagnetic metals.

Abstract

Spin pumping in nonmagnetic/ferromagnetic metal multilayers is studied both theoretically and experimentally. We show that the line widths of the ferromagnetic resonance (FMR) spectrum depend on the thickness of the ferromagnetic metal layers, which must not be in resonance with the oscillating magnetic field. We also show that the penetration depths of the transverse spin current in ferromagnetic metals can be determined by analyzing the line widths of their FMR spectra. The obtained penetration depths in NiFe, CoFe and CoFeB were 3.7 [nm], 2.5 [nm] and 12.0 [nm], respectively.